Chichester Dam

Chichester Dam is a minor concrete gravity dam across the Chichester and Wangat rivers, upstream of Dungog, in the Hunter Region of New South Wales, Australia. The dam's main purpose is water supply for the Lower Hunter region. A mini hydro-electric power station operates at times of peak flow and is connected to the national grid. The impounded reservoir is Lake Chichester.

Location and features
The dam wall is 43 m high, 254 m long, and was constructed using a cyclopean system of interlocking concrete blocks and large boulders with a volume of 91 m3. The wall is anchored to the bedrock below it by 93 stressed tendons. At 100% capacity the dam wall holds back 21500 ML of water at 156.2 m Australian Height Datum. The spillway is capable of discharging 3300 m3/s. The surface area of the reservoir is 1.8 km2 and the catchment area, largely located within the Barrington Tops National Park, is 197 km2. The dam is connected to reservoirs in Maitland, Cessnock and Newcastle by an 80 km gravitation main.

History
Land for the water supply scheme was appropriated in the Gazette of 6 October 1916. To safeguard the purity of the water the populated part of the Wangat Valley, including the old goldmining town of Wangat, and the greater portion of the populated part of the Chichester Valley were resumed. The Act appropriated £A1,049,000 as the estimated cost of construction of the dam, with additional funds set aside for land resumption.

In 1965 the spillway was lowered by 2.75 m to increase flood capacity. In 1985 the dam was post tensioned with cables and the spillway was relocated to the centre of the dam and returned to its original height. In 1995 the seepage potential was reduced under the northern abutment and in 2003 an improved drainage system for the dam's foundations was installed and the left parapet wall was raised to prevent overtopping in a major flood.

Power generation
Following a report by the Health Rivers Commission, in 1998 the Minister for Urban Affairs and Planning, Craig Knowles, announced that a small hydro-electric power station would be installed in the Chichester Dam in order to generate electricity, reduce greenhouse emissions and allow surplus power to be sold back to the grid. Completed in 2001 and operated by Delta Electricity, the mini-power station generates up to 110 kW of electricity at times of peak flow; with an average annual generation of 0.4 GWh.